Cytochrome c, an ideal antioxidant

2003 ◽  
Vol 31 (6) ◽  
pp. 1312-1315 ◽  
Author(s):  
M.O. Pereverzev ◽  
T.V. Vygodina ◽  
A.A. Konstantinov ◽  
V.P. Skulachev
Keyword(s):  
Superoxide Dismutase ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Cytochrome Oxidase ◽  
The Other ◽  
Other Hand ◽  
O2 Reduction

Generation of Δψ (membrane potential) by cytochrome oxidase proteoliposomes oxidizing superoxide-reduced cytochrome c has been demonstrated. XO+HX (xanthine oxidase and hypoxanthine) were used to produce superoxide. It was found that the generation of Δψ is completely abolished by cyanide (an uncoupler) or by superoxide dismutase, and is enhanced by nigericin. Addition of ascorbate after XO+HX causes a further increase in Δψ. On the other hand, XO+HX added after ascorbate do not affect Δψ, indicating that superoxide does not have measurable protonophorous activity. The half-maximal cytochrome c concentration for Δψ generation supported by XO+HX was found to be approx. 1 μM. These data and the results of some other researchers can be rationalized as follows: (1) O2 accepts an electron to form superoxide; (2) cytochrome c oxidizes superoxide back to O2; (3) an electron removed from the reduced cytochrome c is transferred to O2 by cytochrome oxidase in a manner that generates ΔμH+ (transmembrane difference in electrochemical H+ potential). Thus cytochrome c mediates a process of superoxide removal, resulting in regeneration of O2 and utilization of the electron involved previously in the O2 reduction. It is important that cytochrome c is not damaged during the antioxidant reaction, in contrast with many other antioxidants.

scholarly journals The influence of porphyrins on iron-catalysed generation of hydroxyl radicals

1988 ◽  
Vol 250 (1) ◽  
pp. 197-201 ◽  
Author(s):  
J Van Steveninck ◽  
J P J Boegheim ◽  
T M A R Dubbelman ◽  
J Van der Zee
Keyword(s):  
Cytochrome C ◽  
Horseradish Peroxidase ◽  
Experimental Evidence ◽  
Xanthine Oxidase ◽  
Hydroxyl Radicals ◽  
Anion Radical ◽  
The Other ◽  
Haematoporphyrin Derivative ◽  
Other Hand

Uroporphyrin I, haematoporphyrin and haematoporphyrin derivative had no effect on O2-. generation during oxidation of hypoxanthine by xanthine oxidase and on the formation of hydroxyl radicals (OH.) in the hypoxanthine/xanthine oxidase/Fe3+-EDTA/deoxyribose system. On the other hand, these porphyrins strongly inhibited O2-. formation in a horseradish peroxidase/H2O2/NADPH mixture, whereas they augmented OH. generation in this system after addition of Fe3+-EDTA. Experimental evidence suggests that these observations should be ascribed to the formation of a porphyrin anion radical in the horseradish peroxidase/NADPH system. The formation of this anion radical was confirmed by e.s.r. spectroscopy. This radical is apparently unable to reduce cytochrome c, but it can replace O2-. in the OH.-generating Haber-Weiss reaction.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

Photoreception of Paramecium cilia: localization of photosensitivity and binding with anti-frog-rhodopsin IgG

1991 ◽  
Vol 99 (1) ◽  
pp. 67-72
Author(s):  
Y. Nakaoka ◽  
R. Tokioka ◽  
T. Shinozawa ◽  
J. Fujita ◽  
J. Usukura
Keyword(s):  
Membrane Potential ◽  
Polyclonal Antibody ◽  
The Other ◽  
Paramecium Bursaria ◽  
Potential Response ◽  
Light Stimulation ◽  
Intact Cells ◽  
Other Hand ◽  
Immunocytochemical Studies ◽  
Antibody Labeling

Paramecium bursaria is photosensitive and accumulates in a lighted area. The cells can be deciliated by a brief suspension in dilute ethanol. Both intact and deciliated cells showed depolarization in response to light stimulation by a step-increase from dark to above 0.7 mW cm-2 (550 nm). On the other hand, after a step-increase to below 0.4 mW cm-1, intact cells showed hyperpolarization, while the deciliated cells showed no change in membrane potential. This difference in membrane potential response between ciliated and deciliated cells suggests that both somatic and ciliary structures are photosensitive. In our search for the photoreceptive molecules, a polyclonal antibody induced in rabbits against frog rhodopsin was found to cross-react with a 63x10(3) Mr protein of P. bursaria, by immunoelectrophoresis. Immunocytochemical studies showed that the antibody labeling was localized on both the ciliary and the somatic membranes. These results raise the possibility that P. bursaria may contain a rhodopsin-like protein as a photoreceptor molecule.

Comparison of hypoxia-induced contraction in human, monkey, and dog coronary arteries

1992 ◽  
Vol 262 (3) ◽  
pp. H678-H683 ◽  
Author(s):  
N. Toda ◽  
T. Matsumoto ◽  
K. Yoshida
Keyword(s):  
Superoxide Dismutase ◽  
Coronary Artery ◽  
Receptor Antagonist ◽  
Coronary Arteries ◽  
Superoxide Anion ◽  
The Other ◽  
Human Coronary Artery ◽  
Synthesis Inhibitor ◽  
Other Hand

In monkey coronary artery strips contracted with prostaglandin (PG) F2 alpha or K+, exchange of entire N2 for O2 in the gas aerating the bathing media produced a contraction. Endothelium denudation did not alter the response. Aspirin, indomethacin, and ONO 3708, a PG receptor antagonist, markedly inhibited the hypoxia-induced contraction, whereas superoxide dismutase and OKY 046, a thromboxane (Tx) A2 synthesis inhibitor, were ineffective. Diltiazem depressed the contraction. Hypoxia increased the release of PGE2 but not 6-keto-PGF1 alpha and TxB2. Contractions induced by hypoxia of human coronary artery strips were also independent of the endothelium but were suppressed by indomethacin and diltiazem. On the other hand, dog coronary artery contractions induced by hypoxia were attenuated by endothelium denudation but were not influenced by indomethacin. It may be concluded that the hypoxia-induced contraction of monkey and human epicardial coronary arteries is associated with vasoconstrictor PGs released from subendothelial tissues; however, TxA2 and superoxide anion are not involved. The dog coronary artery contraction appears to be elicited by substance(s), other than cyclooxygenase products, released from the endothelium.

Control of proteoliposomal cytochrome c oxidase: the partial reactions

1990 ◽  
Vol 68 (9) ◽  
pp. 1135-1141 ◽  
Author(s):  
Peter Nicholls
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Redox State ◽  
Ph Gradient ◽  
Transfer Model ◽  
State Reduction

The steady-state spectroscopic behaviour and the turnover of cytochrome c oxidase incorporated into proteoliposomes have been investigated as functions of membrane potential and pH gradient. The respiration rate is almost linearly dependent on [cytochrome c2+] at high flux, but while the cytochrome a redox state is always dependent on the [cytochrome c2+] steady state, it reaches a maximum reduction level less than 100% in each case. The maximal aerobic steady-state reduction level of cytochrome a is highest in the presence of valinomycin and lowest in the presence of nigericin. The proportion of [cytochrome c2+] required to achieve 50% of maximal reduction of cytochrome a varies with the added ionophores; the apparent redox potential of cytochrome a is most positive in the fully decontrolled system (plus valinomycin and nigericin). At low levels of cytochrome a reduction, the rate of respiration is no longer a linear function of [cytochrome c2+], but is dependent upon the redox state of both cytochromes a and c. That is, proteoliposomal oxidase does not follow Smith–Conrad kinetics at low cytochrome c reduction levels, especially in the controlled states. The control of cytochrome oxidase turnover by ΔpH and by ΔΨ can be explained either by an allosteric model or by a model with reversed electron transfer between the binuclear centre and cytochrome a. Other evidence suggests that the reversed electron transfer model may be the correct one.Key words: proteoliposomes, cytochrome c, cytochrome oxidase, membrane potential, pH gradient, cytochrome a, electron transfer.

scholarly journals Superoxide dismutase-inhibitible reduction of cytochrome c by the alloxan radical. Implications for alloxan cytotoxicity

1982 ◽  
Vol 207 (3) ◽  
pp. 609-612 ◽  
Author(s):  
C C Winterbourn
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Reduced Glutathione ◽  
Direct Reaction ◽  
Cytochrome C Reduction

Cytochrome c was reduced when superoxide was generated from xanthine oxidase in the presence of alloxan, and by the reaction of alloxan and with reduced glutathione. In each case, most of the reduction was inhibited by superoxide dismutase, but considerably more enzyme was required than with superoxide alone. This indicates that the superoxide dismutase-inhibitible cytochrome c reduction was mainly due to a direct reaction with the alloxan radical, and implies that other reactions that are inhibited by superoxide dismutase could be due to either alloxan radicals or superoxide.

scholarly journals Inhibition of Bacillus anthracis Spore Outgrowth by Nisin

2008 ◽  
Vol 52 (12) ◽  
pp. 4281-4288 ◽  
Author(s):  
Ian M. Gut ◽  
Angela M. Prouty ◽  
Jimmy D. Ballard ◽  
Wilfred A. van der Donk ◽  
Steven R. Blanke
Keyword(s):  
Membrane Potential ◽  
Heat Resistance ◽  
Bacillus Anthracis ◽  
Oxidative Metabolism ◽  
Mode Of Action ◽  
Inhibitory Concentration ◽  
The Other ◽  
Other Hand ◽  
Mechanism Of Inhibition ◽  
Spore Outgrowth

ABSTRACT The lantibiotic nisin has previously been reported to inhibit the outgrowth of spores from several Bacillus species. However, the mode of action of nisin responsible for outgrowth inhibition is poorly understood. By using B. anthracis Sterne 7702 as a model, nisin acted against spores with a 50% inhibitory concentration (IC50) and an IC90 of 0.57 μM and 0.90 μM, respectively. Viable B. anthracis organisms were not recoverable from cultures containing concentrations of nisin greater than the IC90. These studies demonstrated that spores lose heat resistance and become hydrated in the presence of nisin, thereby ruling out a possible mechanism of inhibition in which nisin acts to block germination initiation. Rather, germination initiation is requisite for the action of nisin. This study also revealed that nisin rapidly and irreversibly inhibits growth by preventing the establishment of oxidative metabolism and the membrane potential in germinating spores. On the other hand, nisin had no detectable effects on the typical changes associated with the dissolution of the outer spore structures (e.g., the spore coats, cortex, and exosporium). Thus, the action of nisin results in the uncoupling of two critical sequences of events necessary for the outgrowth of spores: the establishment of metabolism and the shedding of the external spore structures.

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